PHYSICAL PROPERTIES OF SOIL. 217 



CHAPTER VIII. 



PHYSICAL PROPERTIES OF SOIL. 



291. In all attempts at improving soil by manure, 

 two objects are intended, which form the golden rule 

 of applying salts and geine ; to make " heavy land 

 lighter, light land heavier, hot land colder, and 

 cold land hotter." Are there then, notwithstanding 

 all that has been offered and said, differences in soil ? 

 Have not, it may be asked, all the preceding pages 

 been based on the fact, that there is but one soil ? 

 True it has been so said, it is said so now. Chemi- 

 cally, the inorganic elements of all soil are alike. 

 The silicates and salts are nearly the same in all ; the 

 organic portion, the geine varies, and that to a greater 

 degree, than any other ingredient. While the sili- 

 cates compose with great uniformity, from 80 to 90 

 per cent., and the salts of lime, sulphate, and phos- 

 phate, from 1-2 to 3-4 per cent., the geine varies 

 from 1 to 20 per cent. The silicates may be finer 

 or coarser, more sandy or more clayey. All these 

 circumstances, affect, not the chemical, but the phys- 

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